Chapter 3- Tissue Renewal, Regen And Repair Flashcards
What is the difference between tissue regeneration and repair?
Regen- complete reconstitution, structures return to normal (ECM remains intact)
Repair- some deficits (scar formation), damage beyond basal layer
What are the functions of the ECM?
Framework for cell migration
Maintenance of cell polarity
Formation of new blood vessels
Production of GFs, cytokines, chemokines
What is normal cell proliferation regulated by?
Rates of:
Cell proliferation
Cellular differentiation
Apoptotic death
What are characteristics of labile tissues?
Can regenerate as long as stem cell pool is preserved, asymmetric division
What types of tissues are labile?
Epithelium, GI Tracy, oral cavity, ducts
What are the characteristics of quiescent/stable tissues?
Rest in G0 stage but capable of entering the cell cycle, limited capacity to regenerate
What types of tissues are quiescent?
Parenchyma of most solid organs
What are the characteristics of permanent tissues?
Terminally differentiated and non-proliferative, limited stem cells reproduction, not sufficient for regen
What types of tissues are permanent?
Neurons and cardiomyocytes
What drives proliferation?
Signals from GFs and ECM
What is an important source of GFs?
Activated macrophages
What is required for restoration of normal tissues?
Residual scaffolding must be intact
What are the phases of liver regeneration?
Priming- Kuppfer cells produce cytokines, hepatocytes can respond to GFs
GF phase- cells enter G1 and replicate
Termination phase- return to quiescence
What are the characteristics of repair by connective tissue deposition?
Chemokine release
Acute inflammation
Angiogenesis
Granulation tissue formation
Connective tissue remodelling
What is severe, chronic damage to connective tissue/non-dividing cells associated with?
Repair by connective tissue deposition
What factors influence tissue repair?
Infection (prolongs)
Diabetes (limits blood flow)
Nutritional status (vit C deficiency and collagen)
Glucocorticoids (anti-inflam)
Mechanical factors
Poor perfusion
Foreign bodies
Type and extent of injury
What is the difference between primary and secondary union (healing by first or second intention)?
Primary- clean, uninfected wound, minimal fibrosis
Secondary- large, cutaneous ulcer, more inflammation, parenchymal and strongly damage
What are the steps of wound healing?
- Coagulation (clot is scaffolding)
- Neutrophils migrate
- Macrophages dominate
- Granulation tissue fills space (fibroblast migration, ECM proteins and collagen produced)
- Scar retracts
What is fibrosis?
Excessive collagen deposition, usually due to persistent, injurious stimuli, associated with loss of tissue
What disorders may be associated with fibrosis?
Liver cirrhosis
Systemic sclerosis/scleroderma
Idiopathic pulmonary fibrosis
Pneumoconioses
What can result due to inadequate formation of granulation tissue?
Wound dehiscence (rupture)
Ulceration (inadequate vascularization)
What can result due to excessive formation of repair process components?
Hypertrophic scar (deep layers of dermis involved)
Keloid- hypertrophic scar grows beyond wound boundaries
What is exuberant granulation?
Proud flesh
Granulation tissue protrudes above surrounding skin
No actual scar
